Suppression of invasive characteristics by antisense introduction of overexpressed HOX genes in ovarian cancer cells.

HOX genes encode transcription factors that function to establish basic body pattern during embryogenesis and maintain the function of specific organs in the adult. Recent studies have demonstrated that HOX genes are also involved in oncogenesis in a range of malignancies. To elucidate whether HOX genes contribute to ovarian carcinogenesis, we created an expression profile of HOX genes using ovarian derived materials from surgical samples and epithelial ovarian cancer cells derived from five different cell lines. Real-time quantitative RT-PCR assay indicated overexpression of 14 HOX genes in clusters A and B but only 2 genes in clusters C and D. Of the 16 HOX genes, overexpression of paralogs of HOX3, HOX4 and HOX7 is seen in cluster A and B, and of HOX13 in all paralogs. In addition, HOXB7, HOXA13 and HOXB13 showed high levels of overexpression in cancer cells and tissues whereas no or little expression was observed in normal controls. To examine whether overexpressed HOX genes regulate invasion of ovarian cancer cells directly, we introduced an antisense DNA fragment of overexpressed HOXB7 and HOXB13, and HOXC5 that did not show overexpression into SKOV3 cells by electroporation. Antisense introduction followed by chemoinvasion assay using matrigel chamber demonstrated that SKOV3 cells introduced an antisense of each HOXB7 and HOXB13 showed 85% and 50% reduction of invasion ability compared to the parental SKOV3 cells, respectively. In contrast, antisense of HOXC5 introduced cells showed no significant difference of the invasion ability. These results suggest an important role of overexpressed HOX genes, especially for invasive characteristics of ovarian cancer cells.